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DEPARTMENT OF CHEMICAL AND ENVIRONMENTAL ENGINEERING

FACULTY OF ENGINEERING

UNIVERSITI PUTRA MALAYSIA (UPM)

LABORATORY MANUAL

ECH 3902 - CHEMICAL ENGINEERING LABORATORY I

(AMALI KEJURUTERAAN KIMIA I)

SEMESTER 1 2015/2016

Assoc. Prof. Dr. Salmiaton Ali & Dr. Nordin Hj Sabli

Encik Mohamad Rezi bin Hamid

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CONTENTSEXPERIMENT 1: FLOW MEASUREMENTS (WATER) ..................................................................................... 2

EXPERIMENT 2: PUMP TEST RIG .................................................................................................................. 4

EXPERIMENT 3: FRICTION FACTOR IN CIRCULAR PIPES (MANUAL PRESSURE DROP CALCULATION) ...... 6

EXPERIMENT 4: MINOR LOSSES IN PIPES AND FITTINGS (MANUAL PRESSURE DROP CALCULATION) .. 10EXPERIMENT 5: REFRIGERATION SYSTEM ................................................................................................. 13

EXPERIMENT 6: RHEOLOGICAL ANALYSIS (OPEN ENDED) ........................................................................ 16

EXPERIMENT 7: PSYCHOMETRIC PROCESS – HEATING AND COOLING SYSTEM (COMPUTER LINKED AIRCONDITIONING UNIT) ................................................................................................................................. 17

EXPERIMENT 8: FLOW MEASUREMENT (AIR)............................................................................................ 20

EXPERIMENT 9: MARCET BOILER ............................................................................................................... 21

EXPERIMENT 10: BENCH TOP COOLING TOWER....................................................................................... 23

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EXPERIMENT 1: FLOW MEASUREMENTS (WATER)

OBJECTIVE To compare fluid volumetric flow rate measurement between venturi, orifice, rotameter and bench

device

To compare head loss between venturi and orifice

THEORYThe volumetric flow rate Q (m3/s) of any fluid through devices may be expressed by:

= (2 / )/ (1 −( / ) (1.1)

where C d is the discharge coefficient, A1 and A2 are the small and the large cross-sectional area (m 2), Δp is the pressure drop (Pa) and the ρ is the fluid density (kg/m 3)

A common engineering practice is to express the pressure drop as the loss of pressure head h L (metersof fluid) and the acceleration of gravity, g (9.81ms -2)

= ℎ (1.2)

EXPERIMENTAL PROCEDUREStart up1. The schematic representation of the apparatus is shown in Figure 1-1 .2. Open fully the discharge valve of flow apparatus3. Open mid-way the flow control valve of hydraulics bench. Make sure that the discharge hose is

directed to the sump tank (fiber glass) and that the drain valve of the collection tank is left open forthe flow to be discharged back to sump tank

4. Start the pump and allow the flow from the hydraulic bench to the apparatus. Observe the differentwater levels in the manometer board

5. Now close gradually the discharge valve until it is fully closed. Observe that the differentmanometer levels gradually reduce to a leveled datum. Note that the water still flows at a certainpressure difference

6. Now fully open the flow control valve in the hydraulic bench. Observe the rising manometer levels.7. Remove any trapped bubbles by either pressing gradually the plastic tube or taping lightly the glass

tube8. Reduce the water supply by, in alteration, gradually reducing the flow apparatus valve until the

datum level of the manometer is reached

Experiment1. Set a flow rate as measured by the rotameter2. Close drain hole with the rod provided and obtain the collected water volume in sump tank for one

minute by using a stopwatch once the drain hole is fully closed3. Once completed, open the drain hole to avoid spillage.4. At the same flow rate:

4.1 Record the manometer reading to obtain the pressure difference in the venturi tube4.2 Record the manometer reading to obtain the pressure difference in the orifice tube

5. Repeat procedure for different flow rates measured by the flow meter

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DATA COLLECTIONPlease refer laboratory report collection booklet

RESULTS AND DISCUSSIONPlease refer laboratory report collection booklet

Figure 1-1: Installation drawing for flow meter demonstration apparatus

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EXPERIMENT 2: PUMP TEST RIG

OBJECTIVE To measure the amount of head produced by a pump at different pump speed and different

volumetric flow rate

To analyze pump mechanical efficiency

THEORYThe theoretical power P (J/s) required to pump an incompressible fluid through a straight length of apipe with a cross-sectional area of A can be calculated from the definition of powers as the rate ofperforming work (defined as differential force multiply with differential length)

=1

( ) (2.1)

=

where Eqn. 2.1 was rewritten using the definitions of velocity u = l/ t (m/s) and the volumetric flowrate Q = Au (m 3/s)

In practice, however, the actual pump requires power P act that is higher than that calculated by Eqn.2.1. Hence a common method to characterize the operating pump is through the so-called pumpefficiency, defined as:

=P (2.2)

A common engineering practice is to express the pressure drop as the loss of pressure head h L (metersof fluid) and the acceleration of gravity, g (9.81 m/s 2)

= ℎ (2.3)

EXPERIMENTAL PROCEDURESStart Up1. Make sure that the water tank is at least half-filled2. Switch on the power supply on the control panel. The instruments should light up.3. Switch on the followings: pump ‘P1’, process ‘Water’4. Fully open hand valves HV3 & HV4 and close hand valves HV5 & HV65. Fully turn (anti-clockwise) the speed-control potentiometer to the minimum value6. PRECAUTIONS:

7.1 Never operate the pumps when there is no liquid in the pipeline: this may cause seriousdamage to the pump.

7.2 Always monitor the direction of the motor impeller. It should follow the arrow direction onthe pump.

Experiment Part 1: Pump performance at a different pump speed 1. Press the ‘start’ button of the pump

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2. Gradually turn (clockwise) the speed-control potentiometer to a maximum value (approximately1700 RPM) : the pump should operate

3. Wait for a few seconds to allow for steady pumping rate4. Adjust the water flow rate to 100% by opening/closing the ‘check valve’ (this valve opening will not

be changed throughout the entire experiment part 1).

5. Once stabilized, record the flow rate, speed, power and pump head6. Repeat Step 5 with your preset pump speeds

Experiment Part 2: Pump performance at a fixed pump speed1. Press the ‘start’ button of the pump2. Set your pump speed by adjusting the speed-control potentiometer to the maximum value3. Slowly adjust ‘check valve’ fixed so that the flow rate is about 75% of the maximum value4. Wait for a few seconds to allow for steady pumping rate5. Once stabilized, record the flow rate, speed, power and pump head6. Repeat Step 3 - 5 with your preset flow rates (% of the maximum). If required, set to other

intermediate readings

Experiment Part 3: Efficiency comparison between Single Stage and Multi-Stage Pump1. Fully open hand valves HV5 & HV6 and close hand valves HV3 & HV42. Switch on the followings: pump ‘P2’, process ‘Water’3. Fully turn (anti-clockwise) the speed-control potentiometer to the minimum value (choose only one

pump speed)4. Gradually turn (clockwise) the speed-control potentiometer to your preset value: the pump should

operate5. Wait for a few seconds to allow for steady pumping rate6. Once stabilized, record the flow rate, speed, power and pump head7. Turn off the pump. After that, turn off the system



USEFUL INFORMATION

Maximum water pump head (100%) = 6 bar

Maximum water flow rate (100%) = 58.5 L/min

Maximum oil pump head (100%) = 10 bar

Maximum oil flow rate (100%) = 12 L/min

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EXPERIMENT 3: FRICTION FACTOR IN CIRCULAR PIPES (MANUAL PRESSURE DROP CALCULATION)

OBJECTIVE To determine experimentally the friction factor in circular pipes that have different surface

roughness

To investigate the effect of water flow rate on pipe friction factor

THEORYThe friction factor can be calculated using Darcy-Weisbach equation:

=2 ℎ (3.1)

where f D is friction factor, h L is head loss, l is length of pipe, v is velocity of the fluid flow. Thespecifications of the pipe are tabulated in Table 3-1 below:

Table 3-1: List of pipe parameters

Type of PipeLength, l

(m)Internal Diameter, D

(mm)Roughness,

(mm)½” N.B. Smooth Surface 1 13.3 0.000½” N.B. Roughened Surface 1 14.0 0.020

EXPERIMENTAL PROCEDURESStart up1. Figure 3-1 is the schematic drawing of the fluid flow unit2. Connect the inlet of the variable area flow meter to an external pressurized supply3. Connect the water outlet from the drain valve to a suitable drain4. Open all valves on the unit except the vent valve5. Turn on the water supply and allow water to flow through the apparatus6. Close the water outlet valve slightly to provide some back pressure7. Open the vent valve and allow air to escape until water starts to flow through the valve, and then

close the valve8. Press down the center spindle of the non-return manometer connection fitted opposite the pitot-

static probe entry and allow any trapped air to escape9. Close the angle seat valve10. Close the ball valves on the line containing the component required for test11. Adjust the flow rate to 400 L/hr12. The next step follows the water manometer procedure

Procedure 2: Water manometer1. Connect the two inlet pipes of the manometer to the inlet and outlet of smooth surface pipe ( Figure

3-1 )2. Open the vent valve ( Figure 3-2 ) and open the balancing valve on the manometer and vent the

manometer tubes of all air3. Close the vent valve4. Fix the pressure pump onto the manometer and pressurize the manometer until the water levels

in the tubes are at the zero level5. Close the balancing valve.6. Measure the pressure drop across the two tapping by the difference of height7. If required, the pressurization of the manometers can be released by opening the vent valve

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8. Keeping the manometer at the same pipe section, change the flow rates to different flow rates andmeasure the pressure drop values of each flow rate

Procedure 3: Roughened pipe1. Unplug the two manometer inlet pipes and connect to the rough pipe section ( Figure 3-1 )2. Repeat the Steps 3 to 8 in water manometer procedure



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Figure 3-1: Schematic view of the unit

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Figure 3-2: Water and mercury manometer

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EXPERIMENT 4: MINOR LOSSES IN PIPES AND FITTINGS (MANUAL PRESSURE DROP CALCULATION)

OBJECTIVE To find the value of the loss coefficient for several different fitting in pipeline To observe the effect of water flow rate on the value of loss coefficient.

THEORYThe loss coefficient, K L, can be calculated using Darcy-Weisbach equation:

ℎ = ( / 2 ) (3.2)

where h L is head loss, and v is velocity of the fluid flow.

Table 4-1: The pipe components and specification in the pipeline.Components SpecificationsSudden enlargement 13.3 mm to 23.5 mm

Sudden contraction 23.5 mm to 13.3 mm4 elbows 90 , threaded; diameter 13.3 mmBall valve ½” Normal Bore

EXPERIMENTAL PROCEDURESStart Up1. To prepare the unit, use the startup procedures described in Experiment 3 (Start Up: Step 1 to 12)2. Fully open the ball valve and close angle seat valve if student want to measure pressure drop for

component strainer, gate valve, and ball valve3. Fully open angle seat valve and close ball valve if student want to measure pressure drop for

component 90 O bend, elbow and angle seat valve4. To measure orifice and venturi pressure drop open only one valve (angle seat valve or ball valve)5. Connect the manometer inlet pipes to measure the pressure drop across the ball valve6. Follow the water manometer procedure described in Experiment 3 (Water Manometer: Step 3 to

8)7. Take readings for different flow rates8. Repeat step 4 to 6 to measure pressure drop for different pipe fitting



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Figure 4-1: Schematic view of the unit

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Figure 4-2: Water and mercury manometer

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EXPERIMENT 5: REFRIGERATION SYSTEM

OBJECTIVE To determine the effect of condensing temperature and pressure on refrigeration rate and

condenser heat output

To determine the effect of evaporating temperature and pressure on refrigeration rate andevaporator heat output

THEORYA refrigerator is defined as a machine whose prime function is to remove heat from a low temperatureregion. Since energy cannot be destroyed, the heat taken in a low temperature plus any other energyinput must be dissipated to the surroundings. The effect of increasing the condensing temperature onmany refrigeration systems is a reduction in the heat discharged from the condenser and in many casesa smaller reduction in the refrigerating effect at the evaporator.

The rate of heat transfer from refrigerant to water in evaporator can be calculated by:

= ( − ) (5.1)

Where Q e = heat transfer rate, m e = mass flow rate, c p = specific heat of water. The rate of heat transferto water in condenser can be obtained from a similar equation as below

= ( − ) (5.2)

EXPERIMENTAL PROCEDURESStart Up

1.

Procedure 1: Normal Operation2. The schematic drawing of the refrigeration system is shown in Figure 5-1 3. Check all the valves in close positions4. First of all, turn on the cooling water supply and switch on the power to start the unit5. Open the valves indicated in Figure 5-2 for normal operation. This allows vapor to be drawn from

the evaporator by the compressor and for the condensed liquid to return to the evaporator fromthe condenser

6. Open water supply valve and adjust the control valves on the evaporator water flow meter andcondenser water flow meter between 20 to 30 g/s

7. Turn on the main switch and the compressor will start and the two internal lamps will light

Procedure 2: Air venting1. A vent valve is situated on the top of the condenser and this allows air that has been admitted to

the system to be safely vented into void inside the instrument panel.2. To vent air from the condenser, increase the condenser pressure to approximately 50 kN/m 2 above

atmospheric pressure.3. Close the control valve on the condenser water flow meter. This will cause the condenser pressure

to rise.4. Once the 50 kN/m 2 is reached, the vent valve should be briefly opened and the gas will make sound

when entering the void inside the panel.5. Close the valve well before the gauge pressures until it reaches 0 kN/m 2

Procedure 3: Main experiment1. Set the evaporator water flow between 20 to 30 g/s and allow unit to run for about 15 to 20 minutes2. Record all the system parameters

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3. Reduce the condenser cooling water flow rate until the condenser pressure increases byapproximately 10 kN/m 2

4. Allow the unit to stabilize and again record the parameters as in the table5. Repeat for increasing condenser pressure until to the minimum readable value on the condenser

water flow meter is reached, or until the condenser pressure reaches 200 kN/m 2 gauge pressure



Figure 5-1: Refrigeration Cycle Demonstration Unit R633

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Figure 5-2: R633 Valve Position

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EXPERIMENT 7: PSYCHOMETRIC PROCESS – HEATING AND COOLING SYSTEM (COMPUTER LINKED AIRCONDITIONING UNIT)

OBJECTIVE To carry out five thermodynamic processes of air and analyze initial and final air properties using

psychometric chart.

INTRODUCTIONThe experiments consist of 5 parts:

Part 1: Cooling process Part 2: Heating process

Part 3: Humidification process Part 4: Cooling and dehumidification process

Part 5: Heating and humidification process

THEORY

In this experiment, five types of thermodynamics processes are performed on the air-water-vapourmixture using air conditioning unit. These processes include simple heating (raising air temperature),simple cooling (lowering air temperature), humidifying (adding moisture), heating and humidifying(raising air temperature and adding moisture) and dehumidifying (removing moisture). These can bemodelled using the steady-flow conservation of mass and conservation of energy principles:

: , = , (7.1)

: , = , (7.2)

: ℎ − ℎ = − (7.3)

The main parameters of interest include the air flow rate, enthalpy changes, power requirement, andhumidity changes. Note that the subscripts i and o denote the inlet and outlet states, respectively, andthat the water-mass conservation is written as the air-mass conservation via the absolute humidity(ω = kg water vapour/kg dry air).

Of great convenience in determining the properties of moist air is the psychometric chart.Determination of air properties requires measurements of two independent intensive properties, suchas the dry-bulb temperature and wet-bulb temperature.

EXPERIMENTAL PROCEDURES

Start Up1. Read and understand the Hilton air conditioning system (Figure 7-1) 2. Before start experiment, make sure:

2.1 Study Hilton air conditioning system unit2.2 The computer system is turned ON.2.3 The computer software/application for air conditioning unit is running and displaying wet-bulb

temperature, dry-bulb temperature, and air flow rate2.4 The fan is ON2.5 Switch for compressor, air heater, water heater are OFF2.6 Measuring cylinder is empty and clean

3. Choose the air mass flow rate. This can be done by regulating fan rotameter. Ideal air mass flow

rate for this experiment is between 100 g/s to 120 g/s

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4. Measure and record air velocity in the data collection table. For simplicity, air flow rate will not bechanged throughout the entire experiment

ExperimentPart 1: Cooling process

1. Record initial wet-bulb and dry bulb temperature at inlet and outlet point2. Turn on the compressor3. Allow adequate stabilization time for the air cooling process. Monitor the wet-bulb and dry-bulb

temperature change until the system/process stabilized4. Record final wet-bulb and dry-bulb at inlet and outlet point

Note: sampling light is turned on when new data is sent to the PC5. Once completed, switch off the compressor and allow the system to return to its original wet-bulb

and dry-bulb temperature, roughly about 5 minutes

Part 2: Heating process1. Record initial wet-bulb and dry bulb temperature at inlet and outlet point

2. Turn on air heater 3. Allow adequate stabilization time for the air heating process. Monitor the wet-bulb and dry-bulbtemperature change until the system/process stabilized

4. Record final wet-bulb and dry-bulb at inlet and outlet pointNote: sampling light is turned on when new data is sent to the PC

5. Once completed, switch off the air heater and allow the system to return to its original wet-bulband dry-bulb temperature, roughly about 5 minutes

Part 3: Humidification process1. Record initial wet-bulb and dry bulb temperature at inlet and outlet point2. Switch on the electric water heater to heat up the water in the tank. Water vapor will be sprayed

in the spraying section. Be alert of the formation of steam (indicating the formation of water vapor)on the plastic based screen.3. Allow adequate stabilization time for the air humidification process. Monitor the wet-bulb and dry-

bulb temperature change until the system/process stabilized4. Record final wet-bulb and dry-bulb at inlet and outlet point

Note: sampling light is turned on when new data is sent to the PC5. Once completed, switch off the water heater and allow the system to return to its original wet-bulb

and dry-bulb temperature, roughly about 5 minutes

Part 4: Cooling and dehumidification process1. Record initial wet-bulb and dry bulb temperature at inlet and outlet point

2.

Switch on the electric water heater to heat up the water in the tank. Water vapor will be sprayedin the spraying section. Be alert of the formation of steam (indicating the formation of water vapor)on the plastic based screen.

3. At the same time switch on the compressor 4. Allow adequate stabilization time. Monitor the wet-bulb and dry-bulb temperature change until

the system/process stabilized 5. Once the process stabilized:

5.1 Find the rate of water removal. This can be done by collecting water condensate in themeasuring cylinder provided. Allow the condensate to drip until there is continuous drippingas an indicator for process stabilization

5.2 Record wet-bulb and dry bulb temperature at inlet and outlet point Note: sampling light isturned on when new data is sent to the PC

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6. Once completed, switch off the compressor and electric water heater. Allow the system to returnto its original states, roughly about 5 minutes

Part 5: Heating and humidification process1. Record initial wet-bulb and dry bulb temperature at inlet and outlet point

2. Switch on the electric water heater to heat up the water in the tank. Water vapor will be sprayedin the spraying section. Be alert of the formation of steam (indicating the formation of water vapor)on the plastic based screen.

3. At the same time, switch on the air heater4. Allow adequate stabilization time. Monitor the wet-bulb and dry-bulb temperature change until

the system/process stabilized 5. Record final wet-bulb and dry-bulb at inlet and outlet point

Note: sampling light is turned on when new data is sent to the PC6. Once completed, switch off the electric water heater and air heater. Allow the system to return to

its original wet-bulb and dry-bulb temperature, roughly about 5 minutes



USEFUL INFORMATION:Size of outlet opening, m 2 : = 9.5 x 2 cmSize of outlet opening, m 2 : = 20.5 cm

Figure 7-1: Schematic diagram of Hilton air conditioning system unit

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EXPERIMENT 8: FLOW MEASUREMENT (AIR)

OBJECTIVE To compare volumetric flow rate of air measured using venturi with air the actual air flow rate To observe the effect of air flow rate on pressure difference

THEORYThe volumetric flow rate Q (m3/s) of any fluid through devices may be expressed by:

= (2 / )/ (1 −( / ) (8.1)

where C d is the discharge coefficient, A1 and A2 are the small and the large cross-sectional area (m 2), Δp is the pressure drop (Pa) and the ρ is the fluid density (kg/m 3)

A common engineering practice is to express the pressure drop as the loss of pressure head h L (metersof fluid) and the acceleration of gravity, g (9.81ms -2)

= ℎ (8.2)

EXPERIMENTAL PROCEDUREStart up1. Connect the blower/fan to electrical power supply2. Make sure the damper is opened3. Make sure hot wire anemometer is connected to the entire system and turned on4. Turn on the blower

Experiment1. Adjust the damper opening to 25%2. Wait for a few minutes to allow the system to stabilize3. Record the pressure difference and air velocity. Make sure to record the diameter of the venturi

tube and rectangular box4. Repeat Step 2 – 3 with different damper opening

Shutdown1. Turn off the blower/fan

2. Turn off the switch and disconnect electrical wire from the power supply3. Clean the experiment area



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EXPERIMENT 9: MARCET BOILER

OBJECTIVES To establish the relationship between pressure (P) and temperature (T) values of saturated steam. To compare the obtained saturated temperature (T) and pressure (P) with the steam table data.

To find heat of vaporization of water

INTRODUCTIONWhen the room pressure is constant, available liquid in the room will be heated until a certain conditionwhen no matter how much heat is given, the temperature will not increase and the liquid will start tochange into vapor. The temperature remains constant until all liquid is evaporated. Thus, any vaporunder conditions of thermal equilibrium with the liquid from which it originated, has a determinedtemperature at each pressure level. This experiment is to establish the relationship between pressureand temperature values of saturated wet steam.

THEORYThe water inside the boiler is heated up by the electrical resistance and starts to evaporate. As morewater changes phase from liquid to vapor, more vapor accumulates inside the boiler vessel andincreases the pressure imposed on the water surface. This pressure buildup tends to increase theresistance faced by liquid molecules as they change into vapor, consequently increasing the saturationpressure of the remaining liquid.

For a pure substances existing as a mixture of two phases, the Clapeyron relationship relates thepressure, heat and expansion during a change of phase provided that the two phases are in equilibrium.The Clapeyron relationship is:

= −ℎ =ℎ (9.1)

Where;v f = specific volume of waterP = absolute pressurev g = specific volume of steamh fg = latent heat of vaporization = h g - h f h f = enthalpy of waterh g = enthalpy of steam

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Figure 9-1: Marcet Boiler

EXPERIMENTAL PROCEDUREImportant Note: Students must demonstrate an understanding and adhere to safety related to theoperation of machines and workplace at all times.

Start Up1. Setup the boiler for heating and cooling process2. Make sure there is sufficient water inside the Marcet boiler3. Make sure safety valve is open

Experiment1. Start/turn on the Marcet boiler2. After a while, steam will come out from the boiler. Closed the safety valve. This is to purge

trapped air inside the boiler3. Start taking the readings of temperature and relative pressure at intervals of 1 bar, until a relative

pressure that you have chosen.4. Turn off the Marcet boiler. Repeat the steps for cooling process5. Process the results and analyze them.



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EXPERIMENT 10: BENCH TOP COOLING TOWER

OBJECTIVE To determine all “End State” Properties of the Air and H 2O from charts and tables, and the

application of the steady flow equation to selected system to draw up energy and mass balances

(Part 1 and 2) To study the effect of Cooling Load on “Wet Bulb Approach” (Part 3)

EXPERIMENTAL PROCEDURESStartup1. Ensure that the drain cock at rear of load tank is closed, that all switches are off and that the water

control valve (at the bottom of the water flow meter) is fully open2. Check that the unit is level 3. Remove the column (with cap in situ), then carefully pour 3.0 liter water through the square

opening into the basin 4. Refit the column and lightly tighten the knurled nuts

5. Switch on the mains so that the circulating pump runs. If the water flow is less than 40 gs-1

, or ifthe pump is noisy, switch off. It is probable the air is present in the pump.

6. To clear, raise the left hand end of the unit by about 500mm for about 30 sec. Repeat until asatisfactory flow is achieved (Note : The pump must not be allowed to run for a long period until the air has been eliminated)

7. Wetting of the distribution through may be expedited by removing the cap, then moistening thesides with the aid of a tooth brush

8. Pour water into the make-up tank to the gauge mark 9. Remove the plugs from the manometer and check the fluid level. Using the plastic tube supplied,

connect the orifice pressure tapping point in the cap to the left-hand connection on the manometer 10. Fully open the fan inlet shutter and check that the manometer is operating correctly. (The

differential pressure should be about 16mm H 2O. Note that this will be higher for units using a60Hz supply, typically 23mm H 2O) 11. Allow the unit to run for a few minutes for the float valve to adjust the level in the load tank. Top

up the make-up tank as required 12. Check the levels in the wet bulb thermometer reservoirs 13. The unit is now ready for use and may be set to the desired conditions

Note:When the water flow rate is reduced there will be a reduction in the quantity of water held by thepacking and the level in the load tank will rise accordingly, closing the float valve. Although evaporationwill eventually restore the correct level in the load tank, the process can be accelerated by draining off

water from the load tank drain until the level in the make-up tank is seen to fall.

Part 1: Variable Air Flow Rate1. The Bench Top Cooling Tower should be prepared, started and allowed to stabilize under the

following suggested conditions

Orifice differential 16 mm H 2OWater flow rate 40 gs -1

Cooling load 1.0 kW(Note: Stability is reached when there is no further appreciable change in temperature, or flow rate)

2. At regular intervals over a measured period of say 10 minutes, all temperatures and flow ratesshould be noted and the mean values entered on the observation sheet

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3. At the commencement of this period, fill the make-up tanks to the gauge mark with distilled waterAt the end of this period, refill the tank from a known quantity of distilled water in a measuringcylinder

4. By difference, determine the quantity of makeup which has been supplied in the time interval5. Repeat the observation for different air flow rates

Part 1: Different Water Flow Rate1. The Bench Top Cooling Tower should be prepared, started and allowed to stabilize under the

following suggested conditions.


Cooling load 1.0 kW(Note: Stability is reached when there is no further appreciable change in temperature, or flow rate)

2. At regular intervals over a measured period of say 10 minutes, all temperatures and flow rates

should be noted and the mean values entered on the observation sheet3. At the commencement of this period, fill the make-up tanks to the gauge mark with distilled water.

At the end of this period, refill the tank from a known quantity of distilled water in a measuringcylinder

4. By difference, determine the quantity of makeup which has been supplied in the time interval5. Repeat the observation for different water flow rates

Part 3: Different Cooling Load1. The Bench Top Cooling Tower should be prepared, started and allowed to stabilize under the

following suggested conditions


Cooling load 0 kW

2. While keeping the water and air flows constant, the load should be increased to 0.5 kW, and whenconditions have stabilized, the observations should be repeated

3. Similar tests should be made with cooling loads of 1.0 and 1.5kW4. If required, the four tests may then be repeated at another constant air flow

Shutting Down1. Reduce the level in the make-up tank to about 50 mm by running normally

2. Switch off both heaters3. After about two minutes switch off all power supplies4. If the unit is to be idle for several days it should be completely drained

Specimen CalculationsUsing the wet and dry bulb temperatures, point A (air inlet) and B (air outlet) may be plotted on thepsychometric chart, and the following values read off:

Specific Enthalpy at A = h A Moisture content at A = ω A Specific Enthalpy at B = h B Moisture content at B = ω B Specific Volume at B = v aB

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Figure 10-1: Bench top cooling tower system

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